<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>

    <style>
        div {
            width: 600px;
            height: 300px;
            background-color: aquamarine;
            margin: 100px auto;
            display: flex;
            flex-direction: row;
            justify-content: space-between;
        }
        div span {
            display: block;
            width: 100px;
            height: 100px;
            background-color: coral;
            /* flex: 1; */
        }
    </style>
</head>
<body>

    <div>
        <span>1</span>
        <span>2</span>
        <span>3</span>
    </div>
    
</body>
</html>